unexpected

Compared meaning: not expected or not known about beforehand (adjective).

比较义项：事先没有预料到，或没有得到任何通知就发生的（形容词）。

• unexpected 本词

  The general, everyday word for anything that surprises you because you did not expect it; used for people, events, results or feelings, with a neutral, informal tone.

  最通用、最口语化的词，指任何让你感到意外的事，因为事先没有预料到；可用于人、事件、结果或感受，语气中性、随意。

  We had an unexpected visitor knock on our door last night.

  昨晚，一位出乎意料的客人敲了我们的门。

• unforeseen

  More formal; describes circumstances, problems or consequences that could not be predicted or planned for even with care, common in business or official writing.

  较为正式，指即使谨慎规划也无法预见的情况、问题或后果，常见于商务或官方文书中。

  An unforeseen delay pushed the flight back by several hours.

  一个未曾预料到的延误使航班推迟了好几个小时。

• unannounced

  Focuses on the lack of prior notice or warning before someone arrives or something happens, especially visits or inspections, rather than on whether it was predictable.

  强调在某人到来或某事发生之前没有事先通知或警告，尤其用于来访或检查，而不是强调是否可以预测。

  My uncle showed up unannounced at our door last night.

  我叔叔昨晚未经通知就出现在我们家门口。

Unexpected, unforeseen and unannounced all describe something not known about beforehand. Unexpected is the everyday word for any surprise. Unforeseen is more formal, describing problems no one could predict even with care. Unannounced focuses on no prior notice or warning, especially before a visit.

这三个词都可以形容“完全没有预料到”的事，但侧重点不同：unexpected最通用、最口语化，unforeseen更正式，常指即使谨慎规划也难以预见的情况或后果；unannounced则不强调是否能预测，而是强调事先没有任何通知或警告，多用于来访、到达或检查等场合。